Website spec: CSS ratchet in design-lint for reduced-motion, forced-colors, focus-visible, input size, target size (#2915 check 6) #2939

Split from #2915 (checks 1-4, the head/headers/well-known/error-page gate, landed in src/release/webspec.ts, test/webspec.test.ts and bun scripts/smoke.ts <url> --standards). Extend that module and its test; every finding cites its specification.website section.

Done: the design lint fails a stylesheet that animates without a prefers-reduced-motion guard, has no @media (forced-colors: active) handling for its custom focus rings and borders, styles :focus without :focus-visible, sets form inputs below 16px (iOS zoom), or makes an interactive target under 24x24 CSS px (WCAG 2.5.8). As a ratchet: today's count is the ceiling and may only fall.